I think it's enjoyable from the start, but again, the piss poor documentation, and the general low quality of players up from Zulkheim > Qufim > Elshimo can make it difficult, unless you're well versed, or experienced enough to whip newbies into doing your bidding.
They actually have been adding a lot of lower level content lately though. Garrison, BCNM20, mini-Avatar, etc, etc.
The game does evolve a lot, Cheez. Combat system and party formation espically, the kind of jobs you formed with at 25-30ish would get smeared off the map in a LV50-60+ party, Warriors tanking without NIN sub = death.
Speaking of which, tanking becomes a fine art, espically GOOD NIN tanking, not to say PLD's don't bust their asses. Peoples reputations are made and broken over enmity holding compared to the total simplicity of it early on.
Anyway, there's a lot I could say about other stuff, but I'll let someone else do it for now.
"This is what my main problem is. I have a BLM/WHM and the spells are very expensive and there's no return value on them (unlike armor/weapons/accessories)."
Most people at the lower areas don't even equip themselves properly, so it's sorta a one-sided gig for mages, who typically have the smarts to buy all their spells.
At lower levels, it's pretty easy for BLM to -Ga farm however, plus it's fun, and it scares brand newbies to death. Basic NM camping was NEVER for me, even when I was on THF for awhile (till about LV53), so you'll never hear me suggesting that.
Later on, BLM and BRD become basicly impossible to atypically farm with, crafting, mining, BCNM and HNM will be what those jobs do.
Not that I can comment on synthing, sorry. =/ I've never bothered with it much. I will meddle if/when I start up a NIN on the side of my typical Dynamis/HNM/helping routine.
WHM, eh. It has a bad stint as well, but duo farming with a WHM is fun as fuck once you get Hexa, I know that's late in, I just had to say it.
When I was trying to nab my Moldavite ages ago in Onzozo. I always used to see this duo of a Paladin and a White Mage come in and Hexa > Spinning slash into a Light renkei on Cockatrices and shit like that. Inflicting extreme damage on low creatures whose huge asses have way too much HP than they should = fun!
Really, I'm just bitching because I wish BLM and BRD got some farmable WS's as well.
Even early on, it's easy to teleport out to the boonies on WHM, and just farm simple stuff and run errands while you seek or wait for someone, that's one thing I bitched about until I could do on a sub on my BLM until I hit it 72/36.